1. Field of the Invention
The present invention relates to a neodymium-based (Nd-based) two-phase separation amorphous alloy, and more particularly, to a Nd-based two-phase separation amorphous alloy by adding an element having a big difference in heat of mixing in a Nd-based alloy with excellent glass forming ability through an inherent characteristic of compositional elements and consideration of thermodynamics, at the time of forming amorphous phase, to thereby obtain a two-phase separation amorphous alloy during solidification.
2. Description of the Related Art
Amorphous metal can be defined as the atomic positions of the liquid phase are conceptually stopped in view of the structural analysis. Researches on the structural analysis of initial amorphous metal materials have been performed through Roentgen rays or electron diffraction based on a controversy whether the structure of the initial amorphous metal materials are amorphous or crystalline, but the research on the property of materials have not been performed. After 1970, Masumoto and Maddin have succeeded in manufacturing the uniform amorphous ribbon shape with a centrifugal quenching method. Accordingly, measurement about the property of the amorphous material has been facilitated. Since the different magnetic, electric, and mechanical properties are contained in the amorphous materials, in comparison with the conventional metal material, it has been reported that the amorphous materials are the dream metal, to thereby draw the attention of world wide metal and property researchers.
The most important one in the property of the amorphous alloy is the magnetism. The amorphous alloy has been currently developed as practical soft magnetic materials. The reasons why the amorphous alloy is suitable for the magnetic material are as follows.
1) The smaller the crystal magnetic anisotropy constant (K) and magnetism negative constant (λ) may be, the better the magnetic material, may be. It is ideally best that they become all zero. In the case of crystalline materials, Sendust (one of Fe—Al—Si alloys), and Permalloy (one of Fe—Ni alloys) are famous since the values of the crystal magnetic anisotropy constant (K) and magnetism negative constant (λ) are small. However, the composition having the values of zero in these alloys exists as only a point. However, since the amorphous composition meets K≈0, the group of the composition of λ≈0 has a high-permeability and low iron loss characteristic
2) Since the amorphous material is intrinsically of a big electric resistance, the low iron loss can be easily obtained.
3) Since the amorphous material can be made into thin ribbons of 20-30 μm, the low iron loss can be easily obtained.
Research and development on the amorphous materials proceed in the field of the following applications, due to the above-described magnetic property.
a. iron cores of a transformer using a high saturation magnetic flux density, and low iron loss (Fe—B—C or Fe—Si—B alloy)
b. Co-based amorphous alloy (Fe-95Co, Fe—Ni—Co, (Co, Fe)—B—Si) for making a magnetic head, and a magnetic portion for controlling a magnetic core of a switching power supply be near to zero (0)
c. Products including magnetic heads for video cassette recorders (VCR) having many advantages including a high-permeability, a less hysteresis loss, a high electric resistance to thereby cause a low overcurrent loss and an excellent high frequency property, and a high intensity to thereby cause an excellent abrasion resistance
One of the currently developed Nd-based amorphous alloys is a Nd—Fe—B material which is used as a hyper-strong magnet in 1980's. It is known that a very high coercive force can be obtained in a Nd—Fe alloy which has been rapidly cooled. The Nd—Fe alloy has the advantage having the magnetic property which is more excellent than a Sm—Co magnetic material in the room temperature and a price competitive power since the raw material is inexpensive. However, the general chemical composition is near to a Fe-rich composition of Nd15Fe77B8. Moreover, The Nd—Fe alloy has the disadvantage that the magnetic property is drastically lowered according to an increase in the temperature. Thereafter, the alloy of the Nd—Al-TM (TM=transition metal) has been reported. Nd—Al—Fe ternary alloys are under the active research on applications as the ferromagnetic materials (Materials Science and Engineering A Volumes 226-228, June 1997, Pages 393-396).
Particularly, in the case of the conventional Nd-based amorphous alloys as described above, there have been the efforts of controlling alloying elements or a cooling speed for the application of the magnetic material to thereby improve a magnetic property through nano-crystallizing of the whole or the part thereof (Journal of Magnetism and Magnetic Materials Volume 261, Issues 1-2, April 2003, Pages 122-130; Journal of Magnetism and Magnetic Materials Volumes 290-291, Part 2, April 2005, Pages 1214-1216; and Materials Science and Engineering A Volume 385, Issues 1-2, 15 Nov. 2004, Pages 38-43). Here, the nano-crystalline structure in the material suppresses movement of domain walls efficiently, to thereby increase a coercive force and magnetic susceptibility. Demagnetization has a positive effect on a magnetic property through a pinning effect that a corresponding external magnetic field is required. However, the form of precipitate is being limited to a crystal phase through crystallization of the material inside. So far, there have been no reports that the magnetic property can be improved by forming an amorphous phase of a second phase.
In the meantime, in the case of the currently developed two-phase separation amorphous alloys, there have been reports that a phase separation phenomenon is found only in the limited compositional range of Zr—La—Al—Cu—Ni, Y—Ti—Al—Co and Ni—Nb—Y based alloys through a rapid solidification process using a melt spinning process. As a result, while the two-phase separation amorphous alloy needs a higher cooling speed in comparison with a single-phase amorphous alloy. This means that the compositional range of alloy for obtaining amorphous microstructure is limited.